Do You Need a Supercharger or a Turbocharger?
A supercharger or a turbocharger will increase your engine’s overall power between 20 and 40%. However, choosing between the two isn’t always easy. Installation complexity, efficiency for your type of driving, and price all play a factor. To best be able to choose between the two, we need to start with some supercharging and turbocharging basics.
Both superchargers and turbochargers are forced induction systems. They increase power by forcing more air into the engine, which boosts power because it allows for more fuel to be used. If you think about fuel as liquid energy, than it’s easy to see why more fuel in the engine equals more power at the wheels. Turbochargers work by using hot exhaust gases to spin the blades of a compressor mounted to the top of the engine. Superchargers work by attaching to the main drive pulley, using the power of the vehicle’s engine to compress air.
In terms of how much power a supercharger or turbocharger can add, the answer is usually determined by the amount of boost pressure. Boost is the amount of additional air pressure the system adds. A supercharger that only adds 6 lbs of air pressure (aka 6 lbs of boost) isn’t going to add as much power as a turbocharger that’s running at 8.5 lbs of air pressure.
Now that you have the basics, here are some points to consider:
Turbos Are Generally More Efficient…Especially on Smaller Engines
Since turbochargers are powered by your vehicle’s hot exhaust gases, they’re essentially converting wasted energy (hot exhaust gas) into additional power. Superchargers, on the other hand, pull their power directly from the engine. Therefore, superchargers can actually hurt performance at lower RPMs if the power benefits of supercharger boost can be gobbled up by the energy required to drive the supercharger’s pulley. For example: If you’re driving around a big bad V8 pickup truck that can generate massive torque at idle, the power siphoned off by the supercharger’s pulley is a small percentage of the total. If you’re driving around a little 1.6L 4 cylinder, the amount of power needed to drive the supercharger’s pulley can be significant, as smaller engines have a hard time generating much torque at low RPMs.
Therefore, turbos tend to be better suited to small engines where superchargers tend to be better suited to larger engines. Of course, turbochargers aren’t without their shortcomings.
Turbo Lag and More Difficult Installation
Since the turbocharger depends on the exhaust system for power, and since most turbochargers are most efficient at higher engine RPMs, it can take a while for the turbocharger to kick in. This delay is called “turbo lag,” and depending on the vehicle this lag can last a few 10ths of a second or it can last a full 2-3 seconds. The only solution to turbo lag is to use two turbochargers – one that is designed to operate efficiently at very low RPMs, with another turbocharger starting up at higher RPMs to maintain the same overall level of boost across the full RPM range.
As you can imagine, dual turbochargers (better known as twin turbos) are expensive, difficult to calibrate, and frequently beyond the technical capabilities of the average engine customizer. For the most part, the vehicle manufacturer is the only company that can build a quality twin turbo system (only there are some excellent after-market twin turbo kits available for Corvettes). This means that, if your’e adding a turbocharger after-market, you’re probably going to have to live with some turbo lag.
Turbocharger Install is Usually More Difficult
Since the turbocharger needs to be integrated into the existing exhaust system, it can be much more difficult to install after-market than a supercharger that basically bolts on top of the engine. In order to install a turbocharger, you typically need to re-route the exhaust system inside the engine bay so that a turbocharger can straddle the intake and exhaust system. On most engines this is a pretty radical change – if the routing isn’t done correctly, the heat from the exhaust system can impact the performance of the rest of the engine, not to mention reduce reliability.
There are some systems that allow for a turbocharger to be mounted further away from the air intake, thus reducing complexity of the install. However, these systems aren’t as efficient, and in a comparison to a supercharger, these easy-install turbo kits simply aren’t as powerful. Still, they’re not a bad option (learn more about these rear-mounted superchargers by checking out this article about Toyota Tacoma turbochargers as well as the STSTurbo.com website).
Turbochargers vs Superchargers – Which is More Reliable?
The answer to this question often comes down to heat management and cost. As a general rule, most superchargers manage heat better than most turbos. Superchargers that are internally oiled (a pretty common thing on modern S/C’s) are practically bulletproof, whereas superchargers that use the vehicle’s oil system for cooling can be a little less reliable. This is merely because a supercharger using the engine’s oil system could technically experience failure due to oil loss or low oil pressure (which could caused by a clogged filter or an overwhelmed oil pump that can’t keep up at higher RPMs). As you can imagine, internally lubricated superchargers are more expensive that superchargers that utilize the engine’s oil system…spend more money, and reliability is excellent.
Turbochargers have too manage considerably more heat than superchargers for two reasons:
- They’re mounted in the exhaust system, where gas temperatures can reach as high as 2,000 degrees farenheit
- Turbo compressors can spin at as much as 150k RPM, compared to supercharger compressors that could spin as fast as 65k RPM
Turbos can “burn up” pretty quickly if they have a heat problem, and heat problems aren’t always easy to manage during the middle of a race (especially on after-market systems).
Therefore, an after-market supercharger is typically more reliable than an after-market turbocharger, but the more expensive your kit, the lower your risk.
If you’ve got a smaller engine and/or a limited budget, a turbocharger is probably your best option. Just make sure you watch those exhaust gas temps like a hawk, and if you do the install yourself, you need to be extra careful.
If you’ve got a bigger engine or a bigger budget, superchargers are easier to enjoy during daily driving (no turbo lag) and more reliable. In fact, many vehicle manufacturers offer their own fact0ry-backed supercharger kits (Ford Racing and TRD are both good examples).
Finally, check the market before you decide. Some vehicles – like the Miata (for example) – have some very affordable after-market supercharger kits that offer all the great supercharger features at a turbocharged price.